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Cardiovascular > Cardiac Cycle and Special Circulations > Flashcards

Cardiac Cycle and Special Circulations Flashcards

1
Q

when do heart valves produce a sound

A

when they shut

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2
Q

what is the blood flow across the heart

A

SVC-RA-TV-RV-PV-PA-PV-LA-MV-LV-AV-A

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3
Q

what triggers the recurring cardiac cycleof atrial and ventricular contractions and relaxations

A

the orderly depolarisation/ repolarisation sequence

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4
Q

what is the cardiac cycle composed of

A

all events from one heart beat to the next

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5
Q

describe heart in diastole

A

heart ventricle are relaxed and fill with blood

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6
Q

describe the heart in systole

A

heart ventricles contract and pump blood into the aorta (LV) and pulmonary artery (RV)

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7
Q

which side of the heart has a lower pressure

A

left

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8
Q

what are the 5 main events during the cardiac cycle

A

passive filling, atrial contraction, isovolumetric contraction, ventricular ejection, isovolumetric ventricular relaxation

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9
Q

after what does the valve close and why

A

Isovolumetric ventricular Contraction- so volume of blood stays the same

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10
Q

what happens to the mitral valves during ventricular ejection

A

stays closed as blood is ejected into aorta

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11
Q

what happens to the valves during isovolumetric relaxation

A

both closed and ventricle relaxes around volume of blood

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12
Q

what allows passive filling

A

pressure gradient between artia and ventricle (both close to 0)

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13
Q

what fills majority of ventricle

A

80% passive filling, 20% contraction

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14
Q

what does the P wave in the ECG signal

A

atrial depolarisation

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15
Q

when does the artria contract in the ECG

A

between the P wave and QRS

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16
Q

what completes the end diastolic volume

A

atrial contraction

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17
Q

when does ventricular contraction start in the ECG

A

after the QRS (signals ventricular depolarisation)

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18
Q

what causes the AV valves to shut

A

when the ventricular pressure exceeds the atrial pressure

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19
Q

what causes the LUB sound

A

AV valve shutting

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20
Q

describe isovolumetric contraction

A

tension rises around a closed volume

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21
Q

when does the aortic/pulmonary valve open causing ventricular ejection

A

when ventricular pressure exceeds aorta/pulmonary artery pressure

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22
Q

what does the T wave on the ECG signal

A

ventricular repolarisation

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23
Q

what happens to the ventricles after the T wave

A

relax and the ventricular pressure starts to fall

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24
Q

when do the aortic/ pulmonary valves shut after ventricular ejection

A

when ventricular pressure falls below aortic / pulmonary pressure

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25
Q

what produces the secondary heart sound (DUB)

A

closure of aortic/ pulmonary valves after ventricular ejection

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26
Q

what does the valve vibration produce in the aortic pressure curve

A

dicrotic notch

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27
Q

what does closure of aortic/and pulmonary valves signals the start of

A

isovolumetric ventricular relaxation

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28
Q

describe the AV valves during isovolumetric ventricular relaxation

A

shur, tension falls around a closed volume

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29
Q

when do AV valves reopen after isovolumetric ventricular relaxation

A

When the ventricular pressure falls below atrial pressure

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30
Q

what does the first heart sound signal the beginning of

A

systole

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31
Q

what does the second heart sound signal the beginning of

A

diastole

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32
Q

why does arterial pressure never fall to zero

A

as arteries stretch and recoil

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33
Q

when does the JVP occur

A

after right atrial pressure waves

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34
Q

what type of pulse is JVP

A

wave pulse

35
Q

where do the coronary arteries arise from

A

the base of the aorta

36
Q

where does the majority of the venous blood drain from the heart into and via what

A

goes into right atrium via coronary sinus

37
Q

what are the special adaptations of the coronary circulation

A

high capillary density
high basal blood flow
high oxygen extraction under resting conditions

38
Q

what does the high level of oxygen extraction by the myocardium mean for changes in oxygen requirements

A

only way to increase oxygen supply to heart is to increase coronary blood flow

39
Q

what controls coronary blood flow

A

intrinsic and extrinsic mechanisms

40
Q

how do intrinsic mechanisms control coronary blood flow

A

decrease PO2 causes vasodilatation of coronary arterioles in attempt to supply heart with more blood

metabolic hyperaemia

adenosine (produced from breakdown of ATP) is a potent vasodilator

41
Q

what intrinsic mechanisms control coronary blood flow

A

supplied by sympathetic vasoconstrictors
BUT
over ridden by metabolic hyperaemia (as a result of increase HR and SV)

symp stim results in coronary vasodilatation

adrenaline activates beta 2 adrenergic receptors cause vasodilatation and increased blood supply

42
Q

what does stimulation of alpha receptors do

A

vasoconstriction

43
Q

what what stimulation of beta 2 receptors do

A

vasodilatation

44
Q

what stimulates beta 2 receptors

A

circulating adrenaline

45
Q

how does decreased PO2 affect adenonsine and therefore coronary blood flow

A

increases adenosine and increases blood flow

46
Q

how does an increase of metabolites affect coronary blood flow (K+, PCO2, H+)

A

increases blood flow

47
Q

when does peak left coronary flow occurs and why

A

diastole

During contraction of the ventricular myocardium (systole), the subendocardial coronary vessels (the vessels that enter the myocardium) are compressed due to the high ventricular pressures. This compression results in momentary retrograde blood flow (i.e., blood flows backward toward the aorta) which further inhibits perfusion of myocardium during systole

48
Q

what happens to blood supply to the heart if you shorten diastole

A

decreases, coronary blood flow highest in diastole

49
Q

why are the right coronary arteries less affected by contractions of the ventricles/ atrium

A

as right side doesn’t contract as much

50
Q

when does most myocardial perfusion occur

A

in diastole when the subendocardial vessels from the left coronary artery are not compressed

51
Q

what arteries supply the brain

A

internal carotids and vertebral arteries

52
Q

what happens if the grey matter of the brain is starved of oxygen

A

consciousness lost after few seconds of ischaemia, irreversible cell damage within ~ 3 minutes

53
Q

what is the circle of willis

A

basilar (2 vertebral arteries) and carotid arteries anastomose to form circle of willis (vessel ring at base of brain)

54
Q

what arises from the circle of willis

A

major cerebral arteries

55
Q

do brain arteries respond to the barorecptor reflex

A

not necessarily

56
Q

what causes a stroke

A

interruption/ cut off of blood supply to a region of the brian

57
Q

what do auto regulation do and in what ranges does it work

A

autoregulation of cerebral blood flow guards against changes in blood flow if mean arterial blood pressure changes (between 60-160mmHg)

58
Q

does sympathetic stimulation have a big effect on cerebral blood flow

A

no has little effect

59
Q

due to autoregulation what happens to resistance vessels if MABP rises

A

constrict to limit blood flow

60
Q

due to autoregulation what happens to resistance vessels if MABP fall

A

dilate to maintain bloodflow

61
Q

what does a MABP below 50 mmHg cause

A

confusion, fainting and brain damage

62
Q

what effect does increased PCO2 have on the cerebral vessels

A

causes vasodilatation

63
Q

what effect does decreased PCO2 have on the cerebral vessels

A

causes vasoconstriction

64
Q

what is regional hyperaemia

A

blood flow increases to active parts of the brain

65
Q

what is ICP and its normal values

A

intracranial pressure 8-13 mmHg

66
Q

what is CPP and how is it calculated

A

cerebral perfusion pressure (MAP - ICP)

67
Q

what effects does an increasing ICP have on CPP and cerebral blood flow

A

decreases CPP and cerebral blood flow

68
Q

what can increase ICP

A

head injury or brain tumour

69
Q

what is the blood brain barriers

A

cerebral capillaries which have very tight intercellular junctions

70
Q

what are cerebral capillaries highly permeable to

A

O2 and CO2

71
Q

how does glucose pass the BBB

A

by facilitated diffusion using specific carrier molecules

72
Q

what is the BBB exceptionally impermeable to , what does this allow

A

hydrophilic substances such as ions, catecholamines, proteins etc

helps protect brain neurones from fluctuating levels of ions etc in blood

73
Q

how much of cardiac output travels into pulmonary circulation from the right ventricle

A

all of it

74
Q

what meets the metabolic needs to the airways

A

systemic bronchial circulation

75
Q

how much of systemic circulation resistance is pulmonary

A

about 10%

76
Q

how does pulmonary capillary resistance compare to systemic capillary resistance

A

low

77
Q

what adaptation of the pulmonary circulation helps to protect against pulmonary oedema

A

absorptive forces

78
Q

what effect does hypoxia have on pulmonary arterioles

A

vasoconstriction- opposite so that blood is diverted away from poorly ventilated areas of lung

79
Q

what is resting blood flow low

A

because of sympathetic vasoconstrictor tone

80
Q

what overcomes sympathetic vasoconstrictor activity during activity

A

metabolic hyperaemia

81
Q

what changes in the vasculature occur during exercise

A

blood flow to skeletal muscle increases

Metabolic hyperaemia overcomes sympathetic vasoconstrictor activity

Circulating adrenaline causes vasodilatation (beta2 adrenergic receptors)

Plus increased cardiac output during exercise, these could increase skeletal muscle blood flow many folds

82
Q

where do large veins in limbs lie

A

between skeletal muscle

83
Q

what causes varicose veins

A

blood pooling in the lower limbs if venous valves become incompetent

84
Q

why do varicose veins lead to reduce cardiac output

A

because of chronic compensatory increase in blood volume

Cardiovascular (34 decks)

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